They have every right to be free of politics;
However, they chose to accept oversight of the IAEA.
They did not claim the right to pick and chose what rules they wanted.
OTOH, the IAEA can't arbitrarily change the rules, either, which is what they're trying to do.
The NPT is a treaty obligation, and the text of it, linked earlier by TLC, does not support the idea that the IAEA can enforce additional rules without full agreement by Iran, including formal acceptance by their parliament. It also makes no reference whatsoever to "nuclear weapons related activities" that don't involve the use of actual nuclear materials.
Which is not to say that Iran, and likely other NPT states, haven't likely engaged in weapons research. It's just that doing so is outside the realm of the NPT as signed.
So we want Iran to accept additional protocols prohibiting such research, with rather invasive inspection provisions, which sounds fine, but what do we offer in return?
We still deny their right to enrich their own fuel even under additional protocols, which is obvious doublespeak. Netanyahu even demands that they surrender existing enriched materials, as if he has the right to make any demands at all.